1. Field of the Invention
This invention relates to an underground mining system, and more particularly, to a method of mining for developing a longwall panel.
2. Description of the Prior Art
In underground mining, it is well known to continuously dislodge material from a mine face by operation of a continuous mining machine which includes a cutter drum assembly mounted on the front end of the mining machine. The dislodged material is conveyed rearwardly of the cutter drum on the mining machine by a longitudinally extending conveyor. The continuous mining machine continuously advances as material is dislodged from the mine face forming an entry or tunnel in the material seam.
U.S. Pat. No. 3,111,306 discloses a method of mining using a continuous mining machine. A series of substantially parallel entries are driven into the rock formation. A series of substantially parallel rooms are driven at angles to the entries to divide the area to be extracted into tiers of pillars. Then the tunnels are driven in a substantially straight line through the tiers of pillars. After a pillar has been mined, the mined tunnels are caved to relieve pressure on the formation so that the former entries and rooms are lost in the caved area.
In longwall mining parallel, spaced entries are driven into the seam of material to be mined. A mine face is formed between and perpendicular to the spaced apart entries. A shearer-type cutting machine traverses the mine face between the entries. Additional parallel entries are driven to the working face to ventilate the face and provide access thereto for the movement of operating personnel, equipment, supplies, etc. The mined material is transferred to a conveyor that runs parallel to the mine face. The mined material is conveyed laterally to one of the entries and then conveyed or suitably transported therefrom out of the mine. The shearer repeatedly traverses the length of the mine face to dislodge the panel of material to be mined between the mine entries defining the panel.
The continuous mining and longwall mining operations require ventilation of the entries for the supply of air flow to the working face. One approach to face ventilation is the use of a line curtain in an entry, as disclosed in U.S. Pat. No. 4,157,204. A line curtain extends parallel to and is spaced from the walls of an entry, dividing the entry into two parallel passageways. The curtain is mounted between the mine floor and roof. The mining machine is positioned on one side of the curtain. Air flow is directed to the entry to the working face in the passageway where the mining machine is operating. From the working face, the return air is directed to the passageway on the other side of line curtain. In this manner, a continuous flow of air is generated toward and away from the working face.
While it is known to ventilate mine entryways as above-described, there is need in a longwall mining system for efficiently ventilating the working face by the conveyance of air flow to and from the face through the entries driven to the face. However, the entries must also be accessible for the transportation of operating personnel and equipment to and from the face. The movement of personnel and equipment must not interfere with the face ventilation. However, the construction of multiple entries, i.e. more than two, to the working face substantially adds to the cost of the longwall mining operation. Therefore, there is need for a longwall mining system that efficiently uses entryways for face ventilation and the movement of operating personnel and equipment.